• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.142-149
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• 2004

PMLSM(Permanent Magnet linear Synchronous Motor) has widely applied to industrial automations, machine tools and semiconductor equipments due to the merit on the reduction of noise, vibration and the superior dynamic characteristics in comparison to the conventional method, which uses mechanical transfer equipments. Especially, in the case of applying to Z-axis operation structure, control system needs the method of an initial angle setting and the improvement of up/down operation characteristics. This paper proposes an initial angle setting algorithm and a variable gain schedule using real speed and moving direction to improve up/down operation characteristics. The effectiveness of proposed algorithms Is demonstrated by comparing to a conventional gain system via 4-point absolute positions profile with each velocity, acceleration and deceleration.

• Journal of the Korean Magnetics Society
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• v.20 no.2
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• pp.61-67
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• 2010

As a high energy permanent magnet is commonly applied to motors so that small motors have high power capacities, it is also necessary to reduce a cogging torque which causes a noise and vibration in permanent magnet motors. The patterns of cogging torque in permanent magnet motors depend on the magnetic field distributions, so it is possible to reduce a cogging torque by designing a core shapes optimally. But it is known that an optimum design algorithm for reduction of cogging torques is too complicated and the process to get an optimized core shape is time consuming task. In this paper, new simplified core shapes are suggested to reduce a design parameters so that the core shapes to reduce a cogging torques could be obtained with simple computations. The result shows that the cogging torques of permanent magnet motors with this simplified core shapes could be reduced effectively without any loss of average torques.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.739-744
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• 2010

As recent traffic policy focuses on reduction of congestion and environmental contamination, with a catch phrase, 'Green Traffic', Low Carbon Green Growth' and 'Sustainable Development', introducing the new eco-friendly transport means including railway has been emerging as critical issue. Included in the new transport means are BRT, Bimodal Tram and LRT, and this study was intended to evaluate and analyze Bimodal, among others, which generates less emission, noise and vibration thanks to hybrid type traction system employed by Bimodal Tram, which is considered a future-oriented system because of eco-friendly features and cost efficiency as well as punctuality and convenient accessibility to bus. Thus in this study, appropriateness of Bimodal Tram comparing to other system(BRT) was suggested, using conversion traffic from the road, traffic speed and CO2 emission at the metropolitan area and large provincial areas as the barometer in evaluation, and furthermore, the measures applicable to introduction strategy that will meet various functional aspects in urban area in the coming days were developed.

• Journal of Digital Contents Society
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• v.18 no.5
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• pp.989-994
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• 2017

In this paper, we propose a pothole detection system using 2D LiDAR and a pothole detection algorithm. Conventional pothole detection methods can be divided into vibration-based method, 3D reconstruction method, and vision-based method. Proposed pothole detection system uses two inexpensive 2D LiDARs and improves pothole detection performance. Pothole detection algorithm is divided into preprocessing for noise reduction, clustering and line extraction for visualization, and gradient function for pothole decision. By using gradient of distance data function, we check the existence of a pothole and measure the depth and width of the pothole. The pothole detection system is developed using two LiDARs, and the 3D pothole detection performance is shown by detecting a pothole with moving LiDAR system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.493-501
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• 2016

In this study, core technologies of a traction system on a mountain tram operating on the track of mountain road full of sharp curves and steep gradients were developed. In domestic mountain resort areas, sometimes the transportation service is not provided in winter because of ice and heavy snow on roads, so a mountain railway service independent of the climate and geographic conditions is needed. A traction system was designed taking into account of the power of a traction motor to climb the gradient of 120 ‰, which is common in domestic mountainous areas. and power transmission system was designed to consider the installation space for the traction system. In addition, a reduction gear and a propeller shaft were developed. An elastic pinion was developed and applied to the rack & pinion bogie system for steep gradient so that noise and vibration generated by contact between the steel gears could be reduced. Impact comparison tests showed that the vibration level of the elastic pinion is one-third lower than that of previous steel pinion. Independent rotating wheels and axles were developed for the bogie system to operate on the sharp curve of a 10 meter radius. In addition, the band braking system was developed to enhance the braking force during running on the steep gradient. A test for the braking force showed it exerts the required braking force. The performance of the developed core components were verified by the tests and finally they were applied to the bogie system running on the track of steep gradient and sharp curve.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.2
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• pp.119-129
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• 2023

Sleep apnea causes various secondary disease such as hypertension, stroke, myocardial infarction, depression and cognitive impairment. Early detection and continuous management of sleep apnea are urgently needed since it causes cardio-cerebrovascular diseases. In this study, wearable device for monitoring respiration during sleep using PVDF film was developed to detect vibration through trachea caused by breathing, which determines normal breathing and sleep apnea. Variables such as respiration rate and apnea were extracted based on the detected breathing sound data, and a noise reduction algorithm was established to minimize the effect even when there is a noise signal. In addition, it was confirmed that irregular breathing patterns can be analyzed by establishing a moving threshold algorithm. The results show that the accuracy of the respiratory rate from the developed device was 98.7% comparing with the polysomnogrphy result. Accuracy of detection for sleep apnea event was 92.6% and that of the sleep apnea duration was 94.0%. The results of this study will be of great help to the management of sleep disorders and confirmation of treatment by commercialization of wearable devices that can monitor sleep information easily and accurately at home during daily life and confirm the progress of treatment.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.8
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• pp.679-686
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• 2018

In previous paper[1], the authors had compared the current status of European and US rotorcraft development status. In this paper, more detailed procedures have been studied how the European rotorcraft technologies are developed preparing for 21 st century to be more competitive to US. For the systematic procedure to develop next generation aviation technologies including rotorcraft, the pan-European organization, ACARE, was established, and proposed major research agenda for next generation aviation technologies and businesses. Based on the proposed research agenda, all the R&D programs supported by EU are reorganized to be more efficient and competitive. The procedures for the rotorcraft technologies are, first, cabin noise/vibration reduction program (FRIENDCOPTER), second, core technologies to increase of rotor efficiencies and reduce rotor noise (GRC), and then finally to develop fast/long-range next generation rotorcraft (Fast Rotorcraft). As mentioned in previously, all the R&D procedure has to satisfy basic research agenda especially the environmental impact. With theses procedure, the European rotorcraft business had successful achievements not only in current and future market share, but also preparing for next generation rotorcraft platform such as compound and tilt-rotor rotorcraft satisfying market needs.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.4 s.316
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• pp.42-47
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• 2007

To reduce the chattering errors of reed switch sensors in the automatic remote measurement of water meter a reed switch sensor was analyzed and improved. The operation of reed switch sensors can be described as a mechanical contact switch by approximation of permanent magnet piece to generate an electrical pulse. The reed switch sensors are used mostly in measurement application to detect the rotational or translational displacement. To apply for water flow measurement devices, the reed switch sensors should keep high reliability. They are applied for the electronic digital type of water flow meters. The reed switch sensor is just mounted simply on the conventional mechanical type flow meter. A small magnet is attached on a pointer of the water meter counter rotor. Inside the reed sensor two steel leaf springs make mechanical contact and apart repeatedly as rotation of flow meter counter. The counting electrical contact pulses can be converted as the water flow amount. The MCU sends the digital flow rate data to the server using the wireless communication network. But the digital data is occurred difference or won by chattering noise. The reed switch sensor contains chattering error by it self at the force equivalent position. The vibrations such as passing vehicle near to the switch sensor installed location causes chattering. In order to reduce chattering error, most system uses just software methods, for example using filter algorithm and also statistical calibration methods. The chattering errors were reduced by changing leaf spring structure using mechanical characteristics.

• Journal of the Korean Magnetics Society
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• v.25 no.6
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• pp.189-197
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• 2015

As enforced the regulation of fuel efficiency, the electrification of automotive components in internal combustion vehicle has been applied instead of hydraulic pressure. A typical example of such parts is the EPS (electric power steering), and it is applied to most automotive at present. In electric power steering system, the core component is motor. The reduction of cogging torque and torque ripple is required to improve steering feeling and reduce NVH (Noise Vibration Harshness) in EPS. Generally the skewed design of stator or rotor is applied in order to reduce cogging torque and torque ripple. This paper propose the design and analysis methodology of Brusheless PMSM (Permanent Magnet Synchronous Motor) which is applied to skewed stator. The proposed methodology is as follows: First Intial Design PMSM with skewed stator for EPS, Second Optimal design using RSM (Response surface method), Third Performance Analysis such as Phase Back EMF, Inductance, Load torque using FEA (Finite Element Method). Finally, the reliability of proposed design methodology will be verified through the experiments of prototype sample.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.193-198
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• 2004

In general, the function of intake structure, whether it be a open channel, a fully wetted tunnel, a sump or a tank is to supply an evenly distributed flow to a pump station. An even distribution of flow, characterized by strong local flow, can result in formation of surface or submerged vortices, and with certain low values of submergence, my introduce air into pun, causing a reduction of capacity and efficiency, an increase in vibration and additional noise. This study investigated experimentally the formation of the vortex to understand the mechanism of vortex formation and to prevent the formation of vortex in the sump model using by the model test and PIV tool. Sump model was manufactured to 1/8 scale with the drawing of W intake pumping station. from the results of model test and PIV, the vortex were occurred the in the whole section. Thus, sump model tests with the anti-vortex device might be considered to prevent the formation of vortex in the sump model.